Hundreds of thousands of genetically modified mosquitoes are awaiting federal approval for release into the Florida Keys as part of an experiment aimed at reducing the risk of dengue fever.

Mosquito control officials have requested the Food and Drug Administration's sign off on the experiment that would be the first of its kind in the U.S.

Officials are targeting the Aedes aegypti mosquitoes because they can spread dengue fever, a disease health officials thought had been eradicated in the U.S. until 93 cases originated in the Keys in 2009 and 2010.

The trial planned by mosquito control officials and the British company Oxitec would release non-biting male mosquitoes that have been genetically modified to pass along a birth defect that kill their progeny before reaching maturity.

Some residents of the tourist town of Key West worry though on how much research has been done to determine the risks of releasing genetically modified mosquitoes on the Keys' fragile ecosystem.